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• 961-07-9 2'-Deoxyguanosine 

Relevant academic research and scientific papers

Type I and type II photosensitized oxidative modification of 2'-deoxyguanosine (dGuo) by triplet-exicted ketones generated thermally from the 1,2-dioxetane HTMD

The nucleoside 2'-deoxyguanosine (dGuo) was treated with 3-(hydroxymethyl)-3,4,4-trimethyl-1,2-dioxetane (HTMD), the latter generates efficiently triplet-excited carbonyl products on thermal decomposition in the dark. The type I photooxidation products, 2,2-diamino-[(2-deoxy-β-D-erythro-pentofuranosyl)-4-amino]-5(2H)-oxaz olone (oxazolone) and the cyclic nucleoside 2-(S)-2,5'-anhydro-1-(2-deoxy-β-D-erythro-pentofuranosyl)-5-guanidiny lidene-2-hydroxy-4-oxoimidazolidine (oxoimidazolidine), as well as the type II photooxidation products 4-(R)*- and 4-(S)*-4-hydroxy-8-oxo-4,8-dihydro-2'-deoxyguanosine (4-HO-8-oxodGuo) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), were quantitatively determined by appropriate selective and sensitive HPLC assays. The concentration and time profiles revealed that about 40% of the triplet ketones derived from the thermal decomposition of HTMD led to photooxidation of dGuo. Essentially equal amounts of type I and type II photooxidation products were found, as could be established by comparison with predominant type I (benzophenone, riboflavin) and type II (Rose Bengal, methylene blue) photosensitizers. The participation of singlet oxygen (type II activity) was confirmed by the substantial D2O effect in the formation of 8-oxodGuo. The results demonstrate that dioxetanes, particularly HTMD, are efficient photooxidants of dGuo on thermal activation in the dark and constitute excellent chemical tools to study photobiological processes without the use of light, in the present case, photogenotoxicity.

Reaction of Singlet Oxygen with 2'-Deoxyguanosine and DNA. Isolation and Characterization of the Main Oxidation Products

The reaction of singlet molecular oxygen with 2'-deoxyguanosine and DNA was studied. Emphasis was placed on the identification and characterization of the main methylene blue mediated type II (singlet oxygen) oxidation products of 2'-deoxyguanosine and its corresponding 3',5'-di-O-acetylated derivative. Two major oxidation products of 2'-deoxyguanosine were isolated and characterized by mass spectrometry analysis and extensive 1H and 13C NMR measurements as the two 4R* and 4S* diastereomers of 4,8-dihydro-4-hydroxy-8-oxo-2'-deoxyguanosine. The addition of 1O2 was also found to occur to the base moiety of the corresponding 3',5'-di-O-acetylated derivative. Methylene blue mediated photosensitization of 2'-deoxygunosine led also to the production of 7,8-dihydro-8-oxo-2'-deoxyguanosine, but in a relatively lower yield with respect to the two above diastereomers. The participation of singlet oxygen in the mechanism of formation of these oxidation products was confirmed. A reasonable mechanism involving the transient formation of an unstable endoperoxide produced through a Diels-Alder 1,4-cycloaddition of singlet oxygen to the purine ring is suggested. Quantitative analysis allowed us to demonstrate that the two diastereomers of 4,8-dihydro-4-hydroxy-8-oxo-2'-deoxyguanosine are the main singlet oxygen oxidation products of the guanine moiety within nucleosides, whereas 7,8-dihydro-8-oxoguanine was found to be the major 1O2 oxidation product of guanine in double-stranded DNA.